Aaron Joel Santos / Causeway Bay / Hong Kong

Covering an area of more than 1,100 square kilometers, almost three quarters of which is set aside as mountainous park land, Hong Kong ranks fourth in the world when it comes to population density, behind only Macau, Monaco and Singapore. That means a vertical city, which isn’t always obvious at street level. On average, Hong Kong is home to 6,644 people per square kilometer, though that figure, like the apartments themselves, soars astronomically in neighborhoods like Causeway Bay and Mongkok. That’s reflected in the city skyline, which boasts the highest number of skyscrapers in the world. Hong Kong has more than 8,000 buildings that rise above 14 floors, double the number of Manhattan. After the airport moved away from the city center, that reach for the sky became more prevalent on Kowloon side, with the 108-story International Commerce Centre dominating the view towards Hong Kong Island and Two International Finance Centre with its 88 mirrored-glass floors.